1. Field of the Invention
The present invention relates generally to the transition of legacy computing applications and more specifically to a system and method for the access and display of data after transition from a legacy computing application.
1. Description of the Related Art
New application server platforms provide potential improved efficiency and functionality. As a result, legacy applications are often migrated to leading edge technology platforms. In particular, application server platforms compliant with Java 2 Enterprise Edition (J2EE) are increasingly popular. (Java and J2EE are trademarks of Sun Microsystems.) As a result, applications for defining display pages and accessing databases written to be compliant with other application server platforms are in many cases migrated to J2EE-compliant application server platforms.
Often, when this transition from a legacy application occurs, changes are made to legacy database schemas. Enterprises take the transition to a new platform as an opportunity to redefine and enhance existing legacy database schemas. This redefinition of database schemas permits the application on the new platform to exploit the new features available in the new application environment to which the enterprise is migrating its system. Where such restructuring of database schemas occurs, the cost of making the transition may be significant if there are changes to the applications for ensuring that the functionality provided in the legacy application is maintained in the new application.
The cost of such a change is potentially high in cases where legacy applications access relational databases with a defined schema and the defined schema is modified for the new application. For applications in which access in a relational database occurs in web-based display pages, the access is typically by way of relational queries (for example, the SQL SELECT statement). In the context of display pages in web-based systems, update relational operators (for example, UPDATE, INSERT, DELETE statements) are less common. Where display pages are defined against the popular MVC (Model B View B Controller) design pattern, the display pages are intended not to contain update relational operators as such functionality in the display pages is inconsistent with the separation of model, view and controller. Even where present, such updates are typically relatively simple to migrate if present. In contrast, relational database queries may be defined in a complex and intricate manner and the redefinition of such queries for a new schema is a potentially significant undertaking. Although efforts have been made to build tools to assist in rewriting legacy relational database queries for new schemas, the complexity and potential variation of such legacy relational database queries makes the definition and use of such tools for rewriting queries complex and difficult.
As referred to above, legacy applications in web based systems may include defined web-based display pages. Often legacy display pages are defined in a manner inconsistent with the JSP (JavaServer Pages) definition used in J2EE. (JSP is a trademark of Sun Microsystems.) To rewrite such display pages in conformance with a J2EE application server platform is also a potentially complex and costly exercise.
It is therefore desirable to provide a method and system to allow relational queries defined for a database schema in a legacy application to be used after transition to a new database schema and for display pages defined in a legacy application to be used in a system implemented in a J2EE application server platform, without requiring such pages to be rewritten.